Less than 1% quantum defect fiber lasers via ytterbium-doped multicomponent fluorosilicate optical fiber

Abstract

Two ytterbium-doped fiber lasers exhibiting quantum defects of less than 1% are demonstrated, in which pumping at wavelengths of 976.6 and 981.0 nm yielded lasing at wavelengths of 985.7 and 989.8 nm, respectively. The multicomponent fluorosilicate active optical fiber, fabricated using the molten core method, has spectral characteristics similar to those of fluoride glasses, namely short average emission wavelength and long upper state lifetime. A best-case slope efficiency of 62.1% was obtained, matching the theoretical model very well. With further fiber and laser optimization, slope efficiencies approaching the quantum limit should ultimately be possible. A reduction in the quantum defect may offer significant mitigation of issues associated with fiber heating. As such, this work can serve as a possible direction for future scaling of high-power fiber laser systems.

Enhanced CW Lasing and Q‐Switched Pulse Generation Enabled by Tm3+‐Doped Glass Ceramic Fibers

“…In addition, compared with the 808 nm LD, the 1570 nm pump wavelength is closer to the ≈2 µm signal wavelength, enabling a lower laser quantum defect. [ 40 ] The resonator, which consists of a Tm 3+ ‐activated gain fiber, a high‐reflection fiber Bragg grating (HR‐FBG, >99.9%) with a 3 dB bandwidth of 0.4 nm, and a low‐reflection fiber Bragg grating (LR‐FBG, 60%) with a 3 dB bandwidth of 0.05 nm, is incorporated into a copper heat sink to moderate temperature fluctuation. The steps of the connection between gain fiber and FBGs (HR‐FBG and LR‐FBG) are as follows: first, the gain fiber and FBGs are inserted into the silica capillaries and cured with UV adhesive; second, the ends of gain fiber and FBGs are optically polished; thirdly, the gain fiber and FBGs are placed on an optical table and connected precisely by adjusting the 3D adjustable mounts; finally, the connection points between gain fiber and FBGs are cured with UV adhesive.…”

Glass: The carrier of light—Part II—A brief look into the future of optical fiber

“…For reasons of highpower operation, if one remains with silica-based glasses but is not specifically restricted to CVD fabrication, alkaline-earth fluorosilicate glass fibers have exhibited intrinsically low, QD < 1% lasing. 101 Keeping with the focus on fiber materials, specifically glasses, a fascinating approach to thermal management involves laser cooling via anti-Stokes fluorescence (ASF), 102 and its application in "radiation-balanced" lasers, RBLs. 103 In most lasers, best represented by Yb 3+ operating as a quasi-two-level system, the pump energy is greater than the emission energy (ie, the emission wavelength, being longer than the excitation wavelength, is said to be Stokes-shifted).…”

“…That said, the spectroscopy of aluminosilicates has been shown to be favorable 97 as have, more recently, phosphosilicates 100 ; although both these citations use LMA fibers, material and waveguide design effects are convolved. For reasons of high‐power operation, if one remains with silica‐based glasses but is not specifically restricted to CVD fabrication, alkaline‐earth fluorosilicate glass fibers have exhibited intrinsically low, QD < 1% lasing 101 …”

Cladding-pumped Raman fiber laser with 0.78% quantum defect enabled by phosphorus-doped fiber

“…Continuous efforts have been focused on reducing the QD [19][20][21][22][23] . Benefiting from fast development of the high-brightness pump source, Raman fiber laser (RFL) has been rapidly developed and widely investigated in recent years [24][25][26][27] .…”